To reconcile a credit note used to pay invoices and refund in Odoo, you can follow these steps:

1.Create a credit note for the amount of 500 and apply it to the paid invoice of 500. This will result in a balance of 0 for that invoice.
2.Create two new invoices for 200 each.
3.Apply the credit note to both invoices. This will result in a balance of 0 for both invoices.
4.Create a refund for the amount of 100 on the client's credit card.
5.Reconcile the refund with the original payment.

To reconcile items in Odoo, you can follow these steps:

1.Go to Accounting > Reconciliation.
2.Select the bank statement line that you want to reconcile.
3.Select the invoice or payment that you want to reconcile with.
4.Click on "Reconcile".

Once all of the transactions have been reconciled, the customer's account should reflect the correct balances and payments for each invoice.